pub fn dp_rec_mc(amount: u32) -> u32 {
    let changes = [100u32, 50, 30, 20, 10, 5, 2, 1];

    let mut res = 0;
    let mut total = amount;

    for i in 0..8 {
        let temp = total / changes[i];
        total -= temp * changes[i];
        res += temp;
    }
    res
}

// 思路:
// 从大钱开始找
